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Erosion and Sediment Control

What is erosion?

Erosion is recognised as the greatest land degradation issue facing rural Australia. Erosion is basically the dislodgement and movement of soil from one location to another by wind or water. The Ipswich area has some of the most challenging soils in Queensland. Dispersive soils are prevalent in the area and can become a very serious issue when disturbed (e.g. during construction or land disturbance activities).

Management of exposed dispersive soils due to such activities must be considered, as these soils:

  • are very susceptible to most forms of erosion, including raindrop impact, gully, tunnel and stream bank erosion
  • are vulnerable to serious erosion damage in infrastructure like roads, tracks, dams, pipelines, cables and power line corridors
  • are responsible for most of the turbidity in our local waterways
  • can have low fertility and poor soil structure which reduces the ability to re-establish vegetation following disturbances.

Wherever possible, the disturbance of dispersive soils should be avoided. If this is not possible, the following management options should be considered:

  • keep topsoil separate from subsoil when excavating
  • chemical amendments (such as gypsum)
  • compaction
  • runoff management
  • revegetation.

Damage caused by dispersive soils

The following video clip shows a site in Ipswich with highly dispersive soils. The images show the damage caused when the soils are not correctly stabilised following disturbance and the time-lapse clip shows how this soil behaves when wet.

What is sediment?

Sediment is the soil particles collected and transported by water movement, including gravel, sand, silt and clay. Soil which is washed away goes down the storm water drain and usually ends up as sediment in local creeks and rivers. It is the sediment that causes our rivers to become brown, dirty and unhealthy. The amount of sediment entering our storm water system in Ipswich has increased as a result of land clearing and development.

The main sources of sediment in the Bremer River include:

  • erosion from cleared or poorly managed agricultural land
  • erosion from building/construction sites.

Stirred up sediment in rivers and creeks can smother aquatic plants and impact on fish health. Other chemicals in stormwater attach themselves to sediment particles, which means that large amounts of sediment result in more chemicals in the creeks and rivers.

Management and Control of Erosion and Sediment

Residential

Sediment and erosion problems occur throughout the entire Bremer River Catchment area with the majority of sediment coming from cleared agricultural land within rural areas. However, when considering management strategies it is important to realise that urban areas contribute more than twice as much sediment per hectare during rain periods.

How to manage and control erosion and sediment in residential areas:

  • Minimise soil disturbance – if you are undertaking earthworks on your property, considering staging in manageable areas that allow you to clear, work in, then stabilised before progressing to the next stage.
  • Maintain as much grass, mulch and other soil coverage on your property as practical.
  • Stabilise earth batters and other steep areas to control erosion caused by run-off.

More information

Rural

Sediment and erosion problems occur throughout the entire Bremer River Catchment area with the majority of sediment coming from cleared agricultural land within rural areas.

Surprisingly, large quantities of soil can be lost with erosion. One centimetre of soil lost from a one hectare surface area is equivalent to approximately 100 cubic metres of soil being removed, weighing about 100 tonnes. Losses of five to ten centimetres of top soil from many hectares are fairly common during intensive summer rain. In fact, an average ten tonnes per hectare per annum soil loss from cultivation land is considered ‘acceptable. Erosion risk is increased markedly when the soil is in a bare, cultivated condition.

Some of the ways to manage erosion and sediment include:

  • using contour banks and retaining soil cover (mulch)
  • limiting stock access to waterways
  • covering stockpiled soils and landscaping material
  • slowing down water movement.

More information

Building Sites

Large amounts of soil can be lost through erosion - a layer of soil one centimetre deep lost from an average house block is equivalent to approximately five trailer loads of soil. Erosion is worse when there is no grass, plant or mulch cover and soil is left bare. Areas of uncovered soil common when houses are being built are major contributors to this problem in urban areas.

Construction sites are very prone to erosion problems. Council is responsible for ensuring that developers and builders don’t pollute waterways. Council officers patrol the Ipswich area distributing education materials to builders, explaining what they can do to stop soil from leaving their site.

Improving erosion and sediment control (ESC) practises and compliance on construction and building sites is a practical, fair and cost-effective strategy to prevent the amount of sediment run-off and associated costs. Anyone (not just builders) who allows dirt, paint, cement or other chemicals to wash into a stormwater drain can be fined.

All erosion and sediment controls must be in accordance with International Erosion Control Association (IECA) best practice.

How to prevent erosion on house sites:

  • Soil cover – keep the soil on your site covered.
  • Stormwater inlet protection – cover internal stormwater inlets.
  • Downpipes and stormwater diversion – if the roof is on, install downpipes.
  • Waste bin – keep your site clean and tidy.
  • Coarse sediment barrier – install on downslope side and ‘return’ around at ends.
  • Stockpile protection – cover stockpile at the end of each day.
  • Kerb to lot groundcover – cover with turf and keep vehicles off.
  • Capture cement run-off and paint – don’t let it flow down the drain.
  • Entry/exit rock pad – stabilise your site access before work begins.
  • Site inspections and maintenance – regular inspections is essential to ensure measures are working effectively.

Healthy Waterways have developed an easily accessible online toolkit to help you improve erosion and sediment control compliance and reduce sediment pollution in our waterways. Visit Healthywaterways.org/esc

Adopting best-practice erosion and sediment control not only helps keep sediment pollution out of our waterways, it provides the following benefits to builders:

  • saves time and money but not having to clean up sediment or replace lost materials after rain
  • reduces the likelihood of a fine or prosecution for polluting the environment
  • reduces complaints related to dust and stormwater pollution
  • improves relationships and trust with the local council and the community
  • promotes and associates your business with protecting the environment.

Further information on erosion and sediment controls can be found at Healthy Waterways.

More Information

Development sites

With an ever increasing population, the Ipswich area is consistently undertaking extensive clearing of land for urban development projects. Land and infrastructure, including residential, commercial, industrial and public infrastructure developments on land are subject to legal requirements and can have a large impact on water quality in south-east Queensland. Undertaking proper erosion and sediment controls can help protect or enhance environmental values in all Queensland waterways.

All erosion and sediment controls must be in accordance with International Erosion Control Association (IECA) best practice, development approvals and site plans.

When undertaking best practice measures, it is important to include:

  • Site assessment and preparation
    • A site assessment is essential prior to commencement of works. A site assessment should be undertaken by a suitably qualified person and relevant plans/design of erosion and sediment controls should be produced.
    • Development approvals may also have specific conditions in relation to any works and plans.
    • Preparation of site must be in accordance with development conditions and plans, including an erosion and sediment control plan (ESCP).
  • Drainage Control
    • Appropriate drainage controls must be applied to every construction site.
    • Each site is different and thus the required drainage control measures must be assessed on a site-by-site basis.
    • It is important to ensure that stormwater is not unlawfully diverted or released into neighbouring properties, or allowed to cause erosion at discharge points.
  • Erosion Control Measures
  • Sediment Control Measures
  • Dust suppression
  • Site Monitoring and Maintenance
    • Site monitoring should be done on a regular basis by site personnel and any identified issues addressed/corrected.
    • Other site monitoring should be undertaken by a suitably qualified person at regular intervals.
    • Plans, such as an ESCP, need to be reviewed and amended through a development to ensure measures are appropriate for each stage and weather conditions.
    • Any changes to plans or maintenance needs to be undertaken in a timely manner to minimise movement of contaminants into water ways.
    • Sediment basins must be treated, emptied and dewatered within 5 days of the last rain event.

More Information

Complaints

Should you wish to lodge a complaint improper building or other practices resulting in soil erosion or sedimentation issues visit Council's Complaints webpage and follow Council's complaints process.